1. Field of the Invention
The present invention relates to a webbing take-up device that takes up and accommodates a webbing for occupant restraint on a take-up spool, and more particularly to a webbing take-up device capable of turning the take-up spool with driving force of a motor.
2. Related Art
A webbing take-up device is disclosed in, for example, WO2006-123750. In this webbing take-up device, a motive power transmission mechanism (a deceleration mechanism) is provided between a take-up spool and a motor. The motive power transmission mechanism includes a torque limiter mechanism (an overload release mechanism). This torque limiter mechanism includes a large diameter side gear that is turned by driving force of the motor, and a small diameter side gear that is disposed at an inner side of the large diameter side gear and turns interlockingly with the spool. A plural number of limit springs are assembled, side by side in a circumferential direction, to an outer periphery portion of the small diameter side gear. The limit springs have structures that engage with protrusions/depressions formed at an inner periphery portion of the large diameter side gear. Relative rotations between the large diameter side gear and the small diameter side gear are allowed by resilient deformation of the limit springs.
Now, in a webbing take-up device as described above, for reasons such as the need to improve a degree of freedom of layout when the overload release mechanism is disposed at the deceleration mechanism and the like, a reduction in size of the overload release mechanism has been required. There have also been required for that it be made possible to easily adjust an operation torque of the overload release mechanism (a torque required for relatively turning the large diameter side gear and the small diameter side gear) in accordance with changes in the layout as mentioned above.